Circuit for mixing four audio input signals to produce four audio output signals

ABSTRACT

A four channel stereo mixing circuit is disclosed whereby four audio input signals may be mixed in various proportions to yield four audio output signals. The mixing is accomplished through the use of four ring connected potentiometers with the audio input signals applied either to the midpoint of the potentiometers or to the connection point of two potentiometers. The output signals are derived from the moveable terminals of the four potentiometers.

United States Patent [1 1 Odagi [451 Aug. 20, 1974 1 CIRCUIT FOR MIXING FOUR AUDIO INPUT SIGNALS TO PRODUCE FOUR AUDIO OUTPUT SIGNALS [75] Inventor: Kanji Odagi, Osaka, Japan [73] Assignee: Matsushita Electric industrial Co.,

Ltd., Kadoma-shi, Osaka-fu, Japan [22] Filed: July 5, 1972 [21] Appl. No.: 269,085

[30] Foreign Application Priority Data July 8, 1971 Japan 4660535 [52] US. Cl. 179/1 GQ, l79/l00.4 ST, 179/100.1 TD

[51] Int. Cl. H04r 5/00 [58] Field of Search 1 79/15 ET, 1 GO, 100.1 TD, 179/100.4 ST, 1 G, 1 GP, 1 D, 1 VL [56] I References Cited UNITED STATES PATENTS 3,082,295 3/1963 Marsov 179/1 G 3,110,769 11/1963 Bertram 179/1 G 3,170,991 2/1965 Glasgal 179/1 3,632,886 l/l972 Scheiber 179]] GO 3,686,471 8/1972 Takahashi 360/132 3,708,631 [[1973 Bauer 179/1 GO OTHER PUBLICATIONS Four Channels and Compatibility, by Scheiber, AES Preprint, October 1970.

Primary Examinerl(athleen l-l. Claffy Assistant Examiner--Thomas DAmico Attorney, Agent, or FirmWenderoth, Lind & Ponack 57 ABSTRACT A four channel stereo mixing circuit is disclosed whereby four audio input signals maybe mixed in various proportions to yield four audio output signals.

The mixing is accomplished through the use of four ring connected potentiometers with the audio input signals applied either to the midpoint of the potentiometers or to the connection point of two potentiometers. The output signals are derived from the moveable terminals of the four potentiometers.

2 Claims, 6 Drawing Figures PAIENIEDAUGZOISH sum 1 or 2 F/GZ FIG. 4

The present invention relates to a four-channel stereophonic device.

In stereophonic devices, generally, four speakers are arranged in a definite configuration, and each of the speakers reproduces the output of one channel. In such a stereophonic device, the correct sound field cannot be obtained unless the four speakers are arranged correctly as prescribed.

For example, when stereo signals, which are intended to be reproduced by four speakers arranged in a square are reproduced by four speakers arranged in a diamond or in a rectangle, a correct sound field cannot be reproduced, and the reproduced sound field is quite unnatural. The sound field thus obtained rotates or is elongated.

The object of the present invention is to provide a stereophonic device which can reproduce a prescribed sound field regardless of the arrangement of the speakers.

This and other objects and features of the present invention will become apparent from the following description of preferred embodiments thereof, with reference to the attached drawings, in which;

FIGS. 1 to 3 show different arrangements of four speakers in a stereophonic device;

FIG. 4 is a block diagram showing the fundamental construction of the four-channel stereophonic device of the present invention;

FIGS. 5 and 6 are electric circuit diagrams of embodiments of the present invention, illustrating mixing circuits actually used.

In FIG. 1, 1 denotes the listener(s), 2, 3, 4 and 5 denote speakers. In FIG. 1, four speakers 2 through 5 are arranged in a square with respect to the listener(s) 1.

In FIGS. 2 and 3, like parts as in the FIG. 1 are desig nated by like reference numerals. In FIG. 2, four speakers 2 through 5 are arranged in a diamond with respect to the listener(s) 1. In FIG. 3, four speakers 2 through 5 are arranged in a rectangle with respect to the listener(s) 1.

In FIG. 4, numerals 6 to 9 denote input terminals of signals in four respective channels and numerals 10 to 13 denote the output terminals thereof. Numerals 14 through 17 denote mixing circuits, one each of which is inserted in a signal transmission path. Each mixing circuit 14 through 17 mixes the outputs of adjacent channels properly in accordance with the arrangement of the speakers.

It will first be assumed that the signals of each channel applied to the input terminals 6 to 9 are A, B, C and D, and the signals appearing at the output terminals 10 to 13 are W, X, Yand Z. The outputs W, X, Yand Z are applied to the speakers 2, 3, 4 and 5 respectively. The relations between the two signals are as follows:

X=B+cA+dC Y=C+eB+fD Z=D+gC+hA where, a to h are constants.

Accordingly, if the mixing circuits 14 to 17 are adjusted to obtaina=c=e=g=0, and b=d=f=h= l, the signals W, X, Yand Z which appear in the output terminals 10 to 13 are respectively as follows:

An explanation as to how the above relations are obtained will now be made with reference to FIGS. 5 and 6. In FIGS. 5 and 6, like parts as in FIG. 4 are designated by like references. Referring to FIG. 5, the mixing circuits 14 through 17 in FIG. 4 are constituted by four variable resistors 18, 19, 20 and 21 having equal characteristics, which are connected in a series loop form and whose connectionpoints are designated by reference numerals 22, 23, 24 and 25, respectively. Reference numerals 26, 27, 28 and 29 each designate respectively a tap provided at the midpoints of the resistors 18, 19, 20 and 21, respectively, and the input terminals 6, 7, 8 and 9 are connected to the taps 26,27, 28 and 29, respectively. Reference numerals 30, 31, 32 and 33 denote movable contacts. The movable contact 30 is connected to the output terminal 10, and provides movable contact-with the resistor 18. Similarly, the movable contacts 31, 32 and 33 are connected to the output terminals 11, 12 and 13, respectively, and provide movable contact with the resistors 19, 20 and 21, respectively.

When all the movable contacts 30, 31, 32 and 33 are in contact with the taps 26, 27, 28 and 29, respectively, the outputs W, X, Y and Z appearing at the output terminals 10 through 13 are as follows:

Since the signals A, B, C and D are made for the purpose of being applied to the speakers 2, 3, 4 and 5 arranged in a square as shown in FIG. 1, these outputs W, X, Y and Z can be applied to these speakers and thereby the prescribed sound field can be reproduced by the speakers 2 and 5 in FIG. 1.

When the movable contacts 30, 31, 32 and 33 are in contact with the connection points 22, 23, 24 and 25, respectively, the outputs W, X, Y and Z appearing at the output terminals 10 to 13 are as follows:

These signals W, X, Y and Z can be applied to the speakers 2 and 5 arranged in a diamond form as shown in FIG. 2 and thereby the prescribed sound field can be reproduced. As is understood from FIGS. 1 and 2, the signal W to be applied to the speaker 2 in FIG. 2 must be A B for reproducing the prescribed sound field. Similarly, the signals X, Y and Z to be applied to the speakers 3, 4 and 5 in FIG. 2 must be B C, C D and D A, respectively. These demands are satisfied by setting the contacts 30, 31, 32 and 33 being in contact with the connection points 22, 23, 24 and 25, respectively, as described above.

When the movable contacts 30 to 33 are set in contact with the respective resistors 18 to 21 at the positions other than at the taps 26 to 29 and the connection points 22 to 25, respectively, the outputs W, X, Y and Z are as follows:

W A aD k8 X B cA dC Y c @B +fD Z D gC [M By selecting the values of constants a to It so that a d e h O,

b=c=f=g l,

the outputs W, X, Y and Z become as follows:

These outputs can be applied to the speakers 2 to in FIG. 3, and thereby the prescribed sound field can be reproduced. The constants b, c, f and g are determined in accordance with the ratio of the distance be tween the speakers 2 and 3 and the distance between the speakers 2 and 5. It will be understood from FIGS. 1 and 3 that the signal to be applied to the speaker 2 in FIG. 3 must be A bB. Similarly, the signals to be applied to the speakers 3, 4 and 5 in FIG. 3 must be B cA, C +fD and D gC, respectively. These demands are satisfied by setting the contacts 30, 31, 32 and 33 in contact with the resistors 18 to 21, respectively, at

the positions as described above.

Referring to FIG. 6, the mixing circuits 14 to 17 in FIG. 4 are constituted by four variable resistors 34, 35, 36 and 37 connected in series to form a loop. The input terminals 6 to 9 are connected to the connection points 38, 39, 40 and 41 of each two adjacent resistors. Reference numerals 42, 43, 44 and designate movable contacts. The movable contact 42 is connected to the output terminal 10, and provides a movable contact with the resistor 34. Similarly, the movable contacts 43, 44 and 45 are connected to the output terminals ll, 12 and 13, respectively, and provide movable contacts with the resistors 35, 36 and 37, respectively. The operation of the device shown in FIG. 6 is similar to that of the device shown in FIG. 5.

As described hereinbefore, the prescribed sound field can be reproduced by adjusting the mixing circuits regardless of the arrangement of the speakers. The present invention is very advantageous when the arrangement of the speakers is restricted due to the shape of the room where the device is to be set, or by other conditions. Also, the present invention has many advantages. For example, special sound effects can be obtained by deliberately changing the sound field.

In view of the fact that various changes and modifications of the present invention will be apparent to those skilled in the art, such should be construed as being included in the scope of the present invention unless otherwise departing from the true spirit and scope of the present invention.

What is claimed is: l. A four channel stereophonic device comprising four output terminals and four input terminals, said four input terminals being adapted to be connected to four stereo signal sources A, B, C and D, respectively, and first, second, third and fourth mixing circuits, the input of said first mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources D, A and B, the input of said second mix ing circuit being connected to the input terminals adapted to be connected to said stereo signal sources A, B and C, the input of said third mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources 8, C and D, and the input of said fourth mixing means being connected to the input terminals adapted to be connected to said stereo signals C, D and A, the relationship between the inputs and the outputs of said four channel stereophonic device due to said four mixing circuits being:

where A, B, C and D are input signals, respectively, from said signal sources A, B, C and D; W, X, Y and Z are the outputs of said device; and a, b, c, d, e, f, g, and h are constants at least some of which are adjustable, each of said four mixing circuits comprising a potentiometer provided with a tap at the midpoint thereof, two end terminals and a movable terminal, one end terminal of the first one of said four potentiometers being connected to one end terminal of the second of said potentiometers, the other end terminal of said second potentiometer being connected to one end terminal of the third of said potentiometers, the other end terminal of said third potentiometer being connected to the one end terminal of the fourth of said potentiometers, the other end terminal of said fourth potentiometer being connected to the other end terminal of said first potentiometer, said four input terminals being connected, re-

spectively, to said taps of said four potentiometers, and

said movable terminals of said four potentiometers being connected to said output terminals.

2. A four channel stereophonic device comprising four output terminals and four input terminals, said four input terminals being adapted to be connected to four stereo signal sources A, B, C and D, respectively,

and first, second, third and fourth mixing circuits, the input of said first mixingcircuit being connected to the input terminals adapted to be connected to said stereo signal sources D, A and B, the input of said second mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources A, B and C, the input of said third mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources B, C and D, and the input of said fourth mixing means being connected to the input terminals adapted to be connected to said stereo signals C, D and A, the relationship between the inputs and the outputs of said four channel stereophonic device due to said four mixing circuits being:

where A, B, C and D are input signals, respectively, from said signal sources A, B, C and D; W, X, Y and Z are the outputs of said device; and a, b, c, d, e, f, g, and h are constants, each of said mixing circuits comprising a potentiometer having two end terminals and a movable terminal, one end terminal of the first of said potentiometers being connected to one end terminal of the second potentiometer, the other end terminal of said second potentiometer being connected to one end terminal of the third potentiometer, the other end terminal of said third potentiometer being connected to one end terminal of the fourth potentiometer, and the whereb=d=f=h=0. 

1. A four channel stereophonic device comprising four output terminals and four input terminals, said four input terminals being adapted to be connected to four stereo signal sources A, B, C and D, respectively, and first, second, third and fourth mixing circuits, the input of said first mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources D, A and B, the input of said second mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources A, B and C, the input of said third mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources B, C and D, and the input of said fourth mixing means being connected to the input terminals adapted to be connected to said stereo signals C, D and A, the relationship between the inputs and the outputs of said four channel stereophonic device due to said four mixing circuits being: W A + aD + bB X B + cA + dC Y C + eB + fD Z D + gC + hA, where A, B, C and D are input signals, respectively, from said signal sources A, B, C and D; W, X, Y and Z are the outputs of said device; and a, b, c, d, e, f, g, and h are constants at least some of which are adjustable, each of said four mixing circuits comprising a potentiometer provided with a Tap at the midpoint thereof, two end terminals and a movable terminal, one end terminal of the first one of said four potentiometers being connected to one end terminal of the second of said potentiometers, the other end terminal of said second potentiometer being connected to one end terminal of the third of said potentiometers, the other end terminal of said third potentiometer being connected to the one end terminal of the fourth of said potentiometers, the other end terminal of said fourth potentiometer being connected to the other end terminal of said first potentiometer, said four input terminals being connected, respectively, to said taps of said four potentiometers, and said movable terminals of said four potentiometers being connected to said output terminals.
 2. A four channel stereophonic device comprising four output terminals and four input terminals, said four input terminals being adapted to be connected to four stereo signal sources A, B, C and D, respectively, and first, second, third and fourth mixing circuits, the input of said first mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources D, A and B, the input of said second mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources A, B and C, the input of said third mixing circuit being connected to the input terminals adapted to be connected to said stereo signal sources B, C and D, and the input of said fourth mixing means being connected to the input terminals adapted to be connected to said stereo signals C, D and A, the relationship between the inputs and the outputs of said four channel stereophonic device due to said four mixing circuits being: W A + aD + bB X B + cA + dC Y C + eB + fD Z D + gC + hA, where A, B, C and D are input signals, respectively, from said signal sources A, B, C and D; W, X, Y and Z are the outputs of said device; and a, b, c, d, e, f, g, and h are constants, each of said mixing circuits comprising a potentiometer having two end terminals and a movable terminal, one end terminal of the first of said potentiometers being connected to one end terminal of the second potentiometer, the other end terminal of said second potentiometer being connected to one end terminal of the third potentiometer, the other end terminal of said third potentiometer being connected to one end terminal of the fourth potentiometer, and the other end terminal of said fourth potentiometer being connected to the other end terminal of said first potentiometer, said four input terminals being connected, respectively, to the connection points between said four potentiometers, said movable terminals of said four potentiometers being connected, respectively, to said four output terminals, whereby the relation between the input signals and the output signals is: W A + aD X B + cA Y C + eB Z D + gC, where b d f h
 0. 